HERSCHEL, Sir WILLIAM (1738–1822), astronomer, was born at Hanover on 15 Nov. 1738. His great-grandfather, Hans Herschel, a native of Moravia, having embraced protestantism, quitted that country early in the seventeenth century, and became a brewer at Pirna in Saxony. Abraham, Hans's son, was employed in the royal gardens at Dresden. Abraham's youngest son, Isaac, was engaged in 1731 as hautboy-player in the band of the Hanoverian guard, and rose to be bandmaster, but left the regiment with broken health in 1760, and earned a livelihood by giving music lessons until his death, at the age of sixty, in 1767. He married, in August 1732, Anna Ilse Moritzen, by whom he had ten children, of whom Jacob was a member of the king's band at Hanover, and had at least two of his compositions printed in London, and Alexander was summoned to Bath by his brother William, and became a violoncello-player in the Bath orchestra, and at the Three Choirs' festival (cp. Papendick, Journals, i. 252, 270; Annals of the Three Choirs, p. 76); Frederick William, known as William Herschel, was the fourth child.

Brought up, like his three brothers, as a musician, he was at fourteen, when he entered the band of the Hanoverian guards as oboist, an excellent performer both on hautboy and violin. At seventeen his philosophical tastes were already strong, and when in England with the regiment in 1755, he spent all his pay on a copy of Locke ‘On the Human Understanding.’ After the defeat of Hastenbeck, on 26 July 1757, his health began to fail, and his parents privily shipped him off to Dover, where he landed with a French crown-piece in his pocket. The penalties of desertion thus technically incurred were remitted by a pardon handed to him by George III in person at his first interview in 1782. After nearly three years of struggle for bread, Herschel was engaged by the Earl of Darlington to train the band of the Durham militia; and his playing of a violin solo by Giardini at Pontefract in 1760 so delighted Dr. Edward Miller (1731–1807) [q. v.] that he invited him to live with him at Doncaster, and procured for him pupils and conductorships in Wakefield and Halifax (Miller, History of Doncaster, p. 162). Herschel paid a short visit to Hanover in April 1764, and in 1765 was appointed organist at Halifax, defeating competitors by the curious device of weighting the keys to increase the volume of sound. The anecdote is related on Dr. Miller's authority by Southey in the ‘Doctor.’ In 1766 he accepted the ‘agreeable and lucrative situation’ of organist to the Octagon Chapel at Bath, where for many years he directed concerts and oratorios, composed anthems, chants, and whole services, and gave music lessons. Of his compositions the ‘Echo’ catch alone was printed; those preserved in manuscript show no marked individuality.

Herschel, as he told Lichtenberg, had already ‘resolved to place all his future enjoyment’ in the pursuit of knowledge (Göttingische Magazin der Wissenschaften, iii. 4). The study of harmony had led him to mathematics, and he studied Latin, Italian, French, English, and Greek. After fourteen to sixteen hours' teaching he was wont to ‘unbend his mind’ with Maclaurin's ‘Fluxions;’ Smith's ‘Optics’ and Ferguson's ‘Astronomy’ were the companions of his pillow, and inspired his resolution ‘to take nothing upon trust.’ He hired a small reflector, being unable to afford a larger one, bought the tools and patterns of a quaker optician, and with his brother Alexander's help set himself, in 1773, to construct his own instruments. By ‘unremitted endeavours,’ and after two hundred partial failures, the 5½-foot Gregorian was produced, with which, on 4 March 1774, he observed the Orion nebula. The record is preserved at the Royal Society (Journal, No. 1). His twofold ambition was ‘to carry improvements in telescopes to their utmost extent,’ and ‘to leave no spot of the heavens unexamined.’ In 1775 the first of his large reflectors was erected on a grass plot behind his house near Walcot turnpike, and a review of the heavens executed with a Newtonian of 4½ inches aperture. These attempts prompted further exertions; during the intervals of a concert he might be seen running, still in lace ruffles and powder, from the theatre to the workshop. On one occasion, to avoid impairing its form, he polished a speculum without intermission during sixteen hours. In 1780 he removed to a larger house at 19 King Street, and here, on 13 March 1781, in the course of a second review of the heavens, the planet Uranus was discovered. He was then in his forty-third year. Its detection as an object with a small disc was due to the perfection of the seven-foot Newtonian reflector employed. Herschel at first took it for a comet (Phil. Trans. lxxi. 492), but when its true character became known, designated it, in honour of George III (Weld, Hist. Roy. Soc. ii. 146 n.), the ‘Georgium Sidus.’

His first printed paper was an answer in the ‘Ladies' Diary’ for 1780 (p. 46) to a prize question on the vibration of strings; in December 1780, on the invitation of Sir William Watson [q. v.], he joined the Philosophical Society of Bath, contributing several papers to its unpublished ‘Transactions;’ he communicated to the Royal Society on 11 May 1780 ‘Astronomical Observations on the Periodical Star in Collo Ceti’ (Phil. Trans. lxx. 338), and on 11 Jan. 1781 a striking paper on ‘The Rotation of the Planets’ (ib. lxxi. 115). The discovery (then without a parallel) of a new planet was acknowledged by the bestowal of the Copley medal a few days previous to his election into the Royal Society on 6 Dec. 1781. In the spring of 1782 he received a royal summons to bring his instruments to London, when their superiority over those at Greenwich was shown by direct comparison. On 25 May 1782 he had an audience with George III at Buckingham House; on 2 July he exhibited his telescope before the royal family, to the great delight of the king, who was finally induced by Sir Joseph Banks to confer upon him a private appointment as court astronomer, with a salary of 200l. a year.

On 1 Aug. 1782 he removed with his sister Caroline [q. v.] to a large, dilapidated house at Datchet, exchanged in June 1785 for Clay Hall, near Windsor, and that again, on 3 April 1786, for the house and garden at Slough, afterwards known as ‘The Herschels’—‘le lieu du monde,’ Arago wrote, ‘où il a été fait le plus de découvertes.’ Relieved from the ‘intolerable waste of time’ of teaching music, Herschel displayed to the full his prodigious activity. His ‘sweeping’ operations were commonly pursued, regardless of temperature, from dark till dawn. In the course of his third ‘review of the heavens’ in 1783, he often observed four hundred objects, some of them with great care, in a single night. He is stated to have once worked and observed without rest during three days and nights, sleeping at the end twenty-six hours at a stretch. One mirror was never removed from the tube for repolishing until another was ready to take its place, and Miss Herschel relates that ‘the last night at Clay Hall was spent in sweeping till daylight, and by the next evening the telescope stood ready for observation at Slough.’ Many evenings were occupied in transporting telescopes to and from the Queen's Lodge for the purpose of gratifying royal curiosity with views of the heavenly bodies; meetings of the Royal Society were attended when the moon was in the way; funds were supplied by the sale of telescopes. Herschel's polishing machine was perfected in 1788. Before 1795 he had made 200 seven-foot, 150 ten-foot, and 80 twenty-foot, besides a multitude of smaller mirrors. The king paid him six hundred guineas apiece for four ten-foot telescopes, one of them a present for the university of Göttingen, which Herschel delivered personally in July 1786, when he was elected a fellow of the Royal Society of Göttingen, and spent three weeks with his family at Hanover. For a twenty-five-foot telescope, ordered in 1796 for the Madrid observatory, he eventually received 3,150l.; from the Prince of Canino in 1814 2,310l. for a ten-foot and a seven-foot. Innumerable minor commissions were executed. (For the prices of his telescopes see Bode, Jahrbuch, 1788, p. 254; Von Zach, Monatliche Correspondenz, 1802, p. 56; and manuscript Letter Book, pp. 135, 167.)

Herschel pursued meantime with incredible ardour his great object of enlarging telescopic powers. Untoward accidents marred in 1781 his attempts to obtain a thirty-foot mirror; one of forty feet was, however, with the aid of a royal grant of 2,000l., begun at Clay Hall in 1785. His felicity was now complete. He seemed to Miss Burney ‘a man without a wish that has its object in the terrestrial globe.’ She describes him as ‘perfectly unassuming’ yet ‘openly happy’ in his success (Madame d'Arblay, Diary, August 1786).

The discovery, on 11 Jan. 1787, of two Uranian satellites (‘Oberon’ and ‘Titania’), consequent upon the economy of light effected by discarding the small mirror of his twenty-foot (Phil. Trans. lxxvii. 125), determined Herschel to construct his new instrument on the Herschelian or front-view plan. The first great speculum was put into the tube at Slough on 19 Feb. 1787, but proved too thin. A second, cast on 26 Jan. 1788, cracked in cooling. A third was figured by 24 Oct., but not to the satisfaction of its maker, who continued working at it for ten months longer. At the first instant of turning it upon Saturn, on 28 Aug. 1789, a sixth satellite (‘Enceladus’) was detected, and a seventh (‘Mimas’) on 17 Sept. following (ib. lxxx. 10).

A second sum of 2,000l. was in August 1787 granted by George III for the completion of the giant reflector, besides an allowance of 200l. a year for repairs. The tube was 39 feet 4 inches long; the mirror, of 49½ inches diameter, weighed 2,118 pounds. An inclination of about three degrees caused it to throw the image slightly to one side of the tube, where the eye-piece was fixed, the observer standing with his back to the sky. Ladders fifty feet high led to a platform, whence he communicated by means of speaking-tubes with his assistants. Before the optical parts were finished, Miss Herschel narrates, many visitors walked through the tube. Among them was George III, who helped on the Archbishop of Canterbury, saying, ‘Come, my lord bishop, I will show you the way to heaven.’ The definition of this instrument, at first superb, probably fell off later. Since, with a magnifying power of 1,000, it could be made available in England only during about one hundred hours in the year, Herschel estimated that eight hundred years would be needed for a review with it of the whole heavens. The last object upon which it was turned, on 19 Jan. 1811, was the Orion nebula. For thirty-nine years longer it stood with its scaffolding, as represented on the seal of the Royal Astronomical Society, and continued to be designated as a landmark on the Ordnance Survey map of England. But on New-year's eve 1839 a ‘Requiem’ composed by Sir John Herschel was sung by his assembled family within the tube, which was then rivetted up, and laid horizontally on three piers in the garden at Slough, where it still remains, the great speculum adorning the hall of ‘The Herschels.’

Before the completion of the great reflector Slough had become a place of scientific pilgrimage. Piazzi, Lalande, Cassini, Méchain, Legendre, besides princes and grand dukes without number, paid their personal respects to the great astronomer. Von Magellan wrote an interesting account of his methods of observation (Berliner Astr. Jahrbuch, 1788, p. 162); the king of Poland sent him his portrait; the empress of Russia desired specifications of his telescopes; academic distinctions came from all quarters. The university of Edinburgh in 1786, and that of Glasgow many years later, conferred upon him honorary degrees of LL.D.; the American Philosophical Society, the Société Hollandaise, the Academies of Paris, Dijon, Berlin, St. Petersburg, and Stockholm opened their doors to him; he was elected in 1802 a foreign member of the French Institute. He was created in 1816 a knight of the Royal Hanoverian Guelphic order, received the freedom of the city of Glasgow, and his name stands first on the list of presidents of the Royal Astronomical Society.

Herschel married, on 8 May 1788, Mary, only daughter of Mr. James Baldwin, a London merchant, and widow of Mr. John Pitt, by whom she had one son, who died early. She was of a most amiable character, and her jointure relieved Herschel from all pecuniary care. Their only child, John Frederick William Herschel [q. v.], was born on 7 March 1792.

Herschel was a witness for James Watt [q. v.] in the case of Watt v. Bull in 1793, and paid him a visit at Heathfield in 1810. At Paris, in July 1802, he made acquaintance with Laplace, and had an interview with the First Consul. A severe illness in the spring of 1807 permanently impaired his strength, and he was thenceforth obliged to take frequent intervals of rest at Bath, Dawlish (as the guest of Sir William Watson), London, Yorkshire, and Scotland. At Brighton, in September 1813, he met the poet Campbell, who was charmed with his simplicity, kindness, and readiness to explain. ‘He is seventy-six,’ says Campbell, ‘but fresh and stout. … Speaking of himself, he said, with a modesty of manner which quite overcame me …, “I have looked further into space than ever human being did before me. I have observed stars, of which the light it can be proved must take two millions of years to reach this earth”’ (Beattie, Life of Campbell, ii. 234).

Herschel vainly attempted to repolish the four-foot speculum in 1814. As his physical weakness increased his sunny spirits became overcast, his intellect remaining, however, clear to the end. The long series of his communications to the Royal Society closed in his eightieth year, on 11 June 1818, with a paper on the telescopic sounding of space-depths (Phil. Trans. cviii. 429); but he sent to the Astronomical Society, three years subsequently, the places of 145 additional double stars (Memoirs Royal Astron. Soc. i. 166). The latest of his extant autographs is a note, in tremulous character, to his sister, announcing, on 4 July 1819, the appearance of a great comet. He died of bilious fever, on 25 Aug. 1822, in his eighty-fourth year, and was buried in the church of St. Laurence at Upton, near Slough. A mural tablet is inscribed with an epitaph composed by Dr. Goodall, provost of Eton. Lady Herschel died on 6 Jan. 1832, aged 81.

Dr. Charles Burney (1726–1814) [q. v.] speaks strongly of Herschel's social charm and fidelity to his friendships. One of the few hints to be found as to his religious sentiments occurs in an unpublished letter of 27 Feb. 1794, where he says that ‘it is certainly a very laudable thing to receive instruction from the great workmaster of nature, and for that reason all experimental philosophy is instituted’ (Letter Book, p. 201). Music was his favourite recreation; and the vivid enjoyment with which he presided over the gatherings of performers at his house is still traditionally remembered.

The animated expression of Herschel's countenance is well rendered in Abbott's portrait of him at the age of fifty, now in the National Portrait Gallery. A drawing from it by his granddaughter, Lady Gordon, was published in Mrs. John Herschel's ‘Memoir of Caroline Herschel.’ His bust was taken by Lockie in 1787 for Sir William Watson, and a likeness of him, painted by Artaud in 1819, is in the possession of Herschel's grandson, the present baronet.

Herschel's family affections were unusually strong. He threw aside absorbing pursuits at Bath to seek for a younger brother, who had run away from home. He provided for his sister Caroline, and paid her mother for the loss of her services. He supported, for some years previous to his death, Alexander Herschel, his skilful mechanical assistant. Dr. Burney read aloud to Herschel, in 1797–1799, the whole of his ‘Poetical History of Astronomy,’ which, his ‘aversion to poetry’ notwithstanding, obtained his approval. His literary preference was for the prose of Swift. The prolonged succession of Herschel's discoveries and speculations were laid before the Royal Society in sixty-nine memoirs, forming an aggregate unmatched for originality, inventiveness, and power. In nearly every branch of modern physical astronomy he was a pioneer. He was the virtual founder of sidereal science. As an explorer of the heavens he had but one rival, his son. His ‘reviews of the heavens’ afforded him a harvest of 2,500 nebulæ, where 103 had been previously known. He initiated the classification, and indicated a law of distribution of these objects relative to the Milky Way, distinguished the peculiarities of ‘planetary’ and ‘ring-nebulæ’ and ‘nebulous stars,’ and described the occurrence, with an ‘abundance exceeding all imagination,’ of ‘diffused nebulosities’ covering some 152 square degrees of the heavens (Phil. Trans. ci. 275). His views as to the nature of nebulæ underwent a remarkable change. From the ‘resolving’ effects upon many of them of his great telescopes, he at first concluded all to be ‘composed of stars more or less remote’ (ib. lxxix. 212). But the consideration of the ‘typical nebulous star’ in Taurus (Gen. Cat. No. 810) convinced him in 1791 ‘that the nebulosity about the star is not of a starry nature’ (Phil. Trans. lxxxi. 73), but due to the presence of a ‘shining fluid,’ the material likewise of nebulæ of the planetary and diffused kinds, including the Orion nebula. The truth of this inference was demonstrated spectroscopically seventy-three years later. It formed the starting-point for the still dominant theory of stellar development elaborated by him in two memorable papers read before the Royal Society on 20 June 1811 and 24 Feb. 1814 respectively (ib. ci. 269, civ. 248).

‘A knowledge of the construction of the heavens,’ Herschel wrote in 1811, ‘has always been the ultimate object of my observations’ (ib. ci. 269). Its pursuit led him, in Professor Holden's words, to ‘perhaps the grandest scientific conception that has entered the mind of man’ (Life of Herschel, p. 212). The idea of penetrating to the limits of star-filled space, of staking down its boundaries, mapping and surveying it, was of astounding boldness; it was carried out with the patient ardour characteristic of his genius. The method of ‘star-gauging,’ described in 1784 (ib. lxxiv. 445), consisted in counting the number of stars visible in the same telescopic field in different directions, and thence estimating the comparative extent in those directions of the system they form. Its application over 3,400 fields, embracing nearly fifty thousand stars, ‘merely as an example to illustrate the method,’ led him to conclude our sun to belong to a ‘compound nebula’ of a branching form, represented in section by the ‘cloven disc’ sketch (ib. lxxv. 266), since rendered familiar by reproduction. But the principle of star-gauging depended for its validity upon an assumed equable distribution of the stars in space, which, as Herschel was foremost to perceive, did not exist. In 1802 he dwelt on the clustering tendency of Milky Way stars (ib. xcii. 496), twelve years later the hypothesis of ‘equal scattering’ was finally abandoned, and the ‘breaking up of the Milky Way’ under gravitational influences declared to be already far advanced (ib. civ. 282). He did not, however, attempt to replace his superseded ground-plan of the universe, which indeed he seems to have regarded as approximating to its primitive condition. In the memoirs of 1817 and 1818 (ib. cvii. 302, cviii. 429) he dealt with the problem of the ‘universal arrangement in space’ of stars and clusters, introducing, for the purpose of determining relative distances, the ‘equalisation of starlight’ by means of ‘limiting apertures;’ but his arguments involve the inadmissible postulate of a general equality of real stellar lustre.

His discovery of mutually revolving stars was closely connected with his researches into sidereal structure. As a preliminary to attacking by the ‘differential’ method the problem of stellar parallax, and so obtaining a unit of absolute measurement for the stellar system, he early began to collect suitable pairs, and presented to the Royal Society on 10 Jan. 1782 his first catalogue of 269 double stars (ib. lxxii. 112). A quarter of a century's observation enabled him, on 9 June 1803, to define many of them as ‘real binary combinations’ (ib. xciii. 340). In all the six pairs instanced, orbital motion has been confirmed. The occultation of one of the stars of ζ Herculis was observed by him in 1802; he detected the ‘double-double’ character of ε Lyræ (ib. xciv. 373), and noted the contrasted colours of certain pairs. The study of stellar chromatics may indeed be said to have begun with him. He discovered altogether over eight hundred double stars, measuring their ‘angles of position’ by means of the ‘revolving wire micrometer’ invented for the purpose (ib. lxxi. 500), and their angular distances apart with his ‘lamp micrometer.’

Herschel never possessed a transit instrument or ‘equatoreal.’ His telescopes were slung on a scaffolding which rolled on circular rails. They gave consequently only approximate places of the objects he discovered. ‘Designed,’ as Bessel wrote in 1843, ‘to aid vision to the utmost, they were of little use for purposes of measurement. He aimed at acquiring knowledge, not of the motions, but of the constitution of the heavenly bodies, and of the structure of the sidereal edifice’ (Abhandlungen, iii. 470). His discovery in 1783 of the translation of the solar system towards a point in the constellation Hercules (Phil. Trans. lxxiii. 268) was an exception. No more brilliant feat of divinatory genius is on record than his assignment, from the scanty materials at his disposal, of an ‘apex’ for the sun's path within a few degrees of that arrived at by the most refined modern investigations. He returned to the subject in 1805 (ib. xcv. 233) in an essay which, ‘for sustained reflection and high philosophic thought,’ is, in Professor Holden's opinion, ‘to be ranked with the researches of Newton in the “Principia.”’

Stellar photometry took its rise from Herschel's invention of the ‘method of sequences.’ His four ‘Catalogues of comparative brightness for ascertaining the Permanence of the Lustre of Stars’ (1796–9) were rendered available for modern comparisons by C. S. Peirce's reduction of them in 1876 (Annals of Harvard Coll. Observatory, ix. 56). They were completed so as to embrace nearly all Flamsteed's stars, in two manuscript catalogues made known in 1883, together with a journal giving the dates of all the observations. Such as referred to variable stars thus acquired significance (Pickering, ib. xiv. 345; Proceedings of Amer. Acad. xix. 269; Observatory, vii. 256, &c.). Herschel discovered and assigned a period of sixty days to the variations of α Herculis (Phil. Trans. lxxxvi. 452). He ascribed stellar light-fluctuations to the display, through axial rotation, of unequally luminous hemispheres. His comparison in 1798 of the prismatic light of six bright stars was a venture upon new ground of unsuspected fertility (ib. civ. 264).

His theory of the constitution of the sun as a dark, cool body, surrounded by a shell of lucid clouds floating in a transparent atmosphere (ib. lxxxv. 46), held its ground until past the middle of last century. He surmised the periodicity of sun-spots, and attempted to substantiate his idea of a corresponding weather cycle by showing that the price of wheat rose as spots grew scarce (ib. xci. 310). His telescopic scrutiny of the solar surface was all but exhaustive. Among his few illusory observations were those of supposed volcanic outbursts on the moon in 1783 and 1787 (ib. lxxvii. 229) and of four additional Uranian satellites. He, however, established the retrograde revolutions of the pair genuinely seen. His results relative to Saturn, published in six memoirs between 1790 and 1808, included the first determination of its rotation and polar compression, with many observations of great interest on the rings. From recurrent changes of brightness in the fifth satellite (Japetus), he inferred the identity of its periods of rotation and revolution (ib. lxxxii. 14), and found the same law to prevail in the Jovian system. The ‘trade wind’ explanation of Jupiter's belts was suggested by him in 1781 (ib. lxxi. 118); he investigated in 1781 and 1784 the rotation of Mars, and adverted to the analogy between that planet and the earth, demonstrating the general permanence of its markings, and from their seasonal changes the glacial nature of its polar spots (ib. lxxiv. 233). A pungent repudiation in 1793 of Schröter's claim to the discovery of mountains in Venus formed a rare exception to the cordiality of his relations with his contemporaries. His proposal to designate the minor planets as ‘asteroids’ drew upon him a gratuitous attack, probably from Brougham, in the first number of the ‘Edinburgh Review.’ Herschel made important physical observations on the comets of 1807 and 1811, concluding them to be in part self-luminous and of nebular origin.

His discovery of the ‘infra-red’ solar rays renders him illustrious as a physicist. No one before him had suspected the unequal distribution of heat in the spectrum; and he pursued the subject with marvellous sagacity in four papers communicated to the Royal Society in 1800, dealing with the laws of reflection, refraction, and transmission of radiant heat. He traced the ‘heat’ and ‘light curves’ of the solar spectrum with maxima in the infra-red and yellow respectively, and conjectured that ‘the chemical properties of the prismatic colours might be as different as those which relate to light and heat’ (ib. xc. 270).

Herschel's achievements opened a new era in astronomical optics. The importance of large telescopic apertures, as giving proportionate power of ‘space penetration,’ was first by him insisted upon and exemplified, and his specula were as remarkable for perfect figure as for great size. When he began to observe, it was almost unheard of that a star should be seen without ‘rays’ or ‘tails.’ Henry Cavendish happening to sit next Herschel at dinner, slowly addressed him with, ‘Is it true, Dr. Herschel, that you see the stars round?’ ‘Round as a button,’ exclaimed the doctor, when the conversation dropped, till at the close of dinner, Cavendish repeated interrogatively, ‘Round as a button?’ ‘Round as a button,’ briskly rejoined the doctor, and no more was said.
Herschel's extraordinary natural qualifications as an observer were diligently cultivated. ‘Seeing,’ he wrote to Dr. Watson in 1782, ‘is in some respects an art which must be learnt,’ and he compared its practice to that required for playing ‘one of Handel's fugues upon the organ.’ He presents a rarely happy combination of the speculative and experimental faculties, his thoughts transcending, yet eagerly seeking the control of visible facts. ‘As a practical astronomer,’ Professor Holden says, ‘he remains without an equal. In profound philosophy he has few superiors. … His is one of the few names which belong to the whole world.’